Well, I don't know what you mean by feminist; but from an egalitarian stand point there's nothing wrong with reveling in an aesthetic choice IN A PIECE OF FICTION. To paraphrase Dawkins, "fiction...it's fake. Bitches."
I'm sorry, I just really hate this double standard. Leonidas is tits naked in '300' and I never heard so much as a grumble from anybody. Men don't complain because...the '300' Spartans were playing up their testosterone kindled confidence in battle. Boasting their near invincibility as eugenically bred super soldiers. They were taunting the enemy. Why can't women do the same thing? Why does it always have to come down to exploitation?
Celtics wore next to no armor in combat; and they put all of central Europe under their feet for 300 years. If we're going to argue practicality then let's also argue reality. Historically many great warrior cultures didn't wear restrictive armor. Armor is freaking expensive; not everyone can afford it.
This is just the history nerd in me talking. I don't think you're any less sexually progressive just because you like you some man candy or a titillating medieval ensemble.